Firing circuit for ignitrons



. May 28, 1946;

w. PAKALA FIRING CIRCUIT FOR IGNI TRONS 2 Sheets-Shegt 1 Filed July l9, 1940 mm mt a P E. .m & Z w

ATTORNEY v vMay ,1946. W..'E.-PAKI.\ILA H v 2;40 1, 01 3 FIRING CIRCUIT FOR IGNITRONS Filed July 19, 1940 2 Sheets-Sheet 2 ATTORNEY WITNESSES: D mvzmon I Wz'ZZiamZfPatala. BY I kmww Patented May 28, 1946 Ul'lED STATES PATENT OFFICE FIRING CIRCUIT FOR IGNITRON S William E. Pakala, Forest mu rs... assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 19, 1940, Serial No. 3%,287 4 Claims. (Cl. 315-141) My invention relates to vapor electric conv verters and particularly to a control system for controlling the instant of ignition of a makealive type valve. I

In the operation of vapor electric devices such as make-alive type valves considerable difficulty has been experienced in securing proper application of the control potentials to the make-alive electrode for initiating the conducting'cycle in the valve. Heretofore it has been customary to use mechanical contact devices or auxiliary electric valves for applying the make-alive potential to the make-alive electrode. It has also been proposed to utilize so-called peaked wave generators for app ying potential to the'make-alive electrodes. These prior devices have had certain'disadvantages in that the auxiliary valves .were of short life and consequently required replacing at frequent intervals. Contact devices were also unsatisfactory in that the contact points were readily burned or destroyed in operation.

I have found that satisfactory operation can be secured by utilizing a normal alternating current control source and distorting the wave form by means of suitable saturable reactors to produce a so-ca1led peak wave for applying to the make-alive electrode.

It is therefore an object of my invention to provide a control system utilizing saturable reactors to control the application of a peaked impulse to-the make-alive electrode.

It is a further object of my invention to provide a cheap and reliable control device for a vapor electric device.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

Figure 1 is a schematic illlustration of a vapor electrlc converter according to my invention;

Fig. 2 is a diagrammatic illustration of the wave -form as secured by my improved impulsing' device, and v v Fig. 3 is a modification according to my invention.

In an exemplary embodiment of my invention according to Fig. 1, an alternating current circuit l is connected to a direct current .circuit 2 by means of a suitable rectifier transformer 3,

the flow of current through the transformer being regulated by means of the vapor electric converter composed of a plurality of make-alive type valves 4. Each valve 4 includes a vaporizaole cathode 5 of suitable material such as mercury, a.cooperating anode 6, a suitable shield 1 enclosing the anode 8 and a make-alive electrode 8 in contact with or partially immersed in the cathode 5. 5 The control system according to my invention comprises a suitable alternating-current source shown in the form of a control transformer 9 having a plurality of secondary phase windings l corresponding in number to the make-alive electrodes 8 to be controlled. The primary H of the control transformer 8 is connected in any suitable alternating current source such as the alternating current circuit l.' Preferably a phase shifting device such as the induction phase shifter I2 is inserted between the alternating cur rent source I and the primary H of the control transformer 9.

As the control transformer 9 produces a substantially sinusoidal wave shape, and as a steeply 20 rising or peaked wave shape is desirable for application to the make-alive electrode, I have introduced a saturable reactor I3 which includes a winding It in series between the phase terminals l of the control transformer 9 and the asso- 25 ciated make-alive electrodes 8. Each series winding it is associated with a magnetic core l6 of a material having high permeability and a sharp saturation point. Preferably a suitable unidirectional conductor or asymmetrically conduct.- 3 ing device I! or rectifying device is inserted in series with the make-alive electrode 8 so that the control impulses of only the desired polarity are conducted to the make-alive electrodes 8. In order to block out the inverse potential from the make-alive electrode 8, while still permitting the flow of the inverse current-impulses in the reactor-winding l4 and in the transformer-winding l0, producing therein a symmetrical alternating current without any direct-current component in said reactor-winding M or said transformerwinding lo, a suitable unidirectional conductor or asymmetrically conducting device 18 is usually inserted in shunt with the make-alive electhe saturable reactor I3 alone.

current will be sufllcient to saturate the core l8 of the reactor,whereby a discontinuity in the saturation-curve of the reactor is obtained at said portion of each ositive and negative impulse, and a rapid increase in current takes place to produce a strongly peaked wave form 20 as diagrammatically illustrated in Fi 2.

The series rectifier l'l permits the passage of a half-wave of this potential 20 to the makealive electrode 8 while the shunt rectifier l8 shunts out the inverse half-cycle so that during the forward half-cycle a cathode spot will be formed in the valve 4 by the flow of potential through the series rectifier l1 and the make-alive electrode 8 and during the inverse half cycle there will be no action at the make-alive electrode 8.

In order to permit ready pick up of the main arc from the anode 6, the'shield I is connected to a suitable source of in-phase potential herein "illustrated as the anode circuit. After the formation of the cathode spot a preliminary discharge will take place from the anode shield 1 thus ionizing the anode space and permitting the ready pick up of the current carrying arc to the anode 6.

In the'modiflcation of my invention according to Fig. 3 suitable capacitors 2| have been connected in series with the winding l4 of the saturable reactors I3 to produce a steeper impulse of shorter duration than is secured by means of A steep wavenected in shunt-circuit relation around said make-alive electrode and said series asymmetrically conducting device, whereby a path is provided for unidirectional-current impulses oi the other polarity; said alternating-current source and said reactor adapted to carry substantially symmetrical current-impulses, with the currents in opposite directions substantially equal to each other.

2. A make-alive control-system comprising a vapor-electric valvedevice, an alternating-current source; an inductance-device having a saturable core; a series asymmetrically conducting device; a shunting asymmetrically conducting device; circuit-means, including said alternatingcurrent source, for impressing upon said inductance-device an alternating voltage having sub-' stantially equal positive and negative impulses.

said impulses having suflicient magnitude to saturate the inductance-device at a portion of each of the positive and negative impulses, whereby a discontinuity in the saturation-curve of the inductance-device is obtained at said portion of each positive and negative impulse; make-alive circuit-means, including said series asymmetrically conducting device, for utilizing said inductance-device to cause peaked positive current-impulses to be supplied to a make-alive electrode of said valve-device; and a shunting circuit, including said shunting asymmetrically conducting device, connected in shunt-circuit relation around said make-alive electrode and said series asymmetrically conducting device, whereby a path is provided for the peaked negative current-impulses.

3. A control system comprising, an altemating-current source; an inductance-device havregardless of the condition of the make-alive electrode, thus making the operation of the vaporelectric valves 4 more uniform anode shields I- have been connected to a source controllable in phase with relation to the potential applied to the main anode. While any suitablesource of, control potential can be utilized, I prefer to use an intermediate tap 22 on each of the phase windings ID of the control transformer 9 to secure a suitable potential for application to the anode shield 1.

While forpurposes of illustration I have shown and described specific embodiments of my invention, it will be apparent that changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. A make-alive control-system comprising a vapor-electric valve-device: an alternating-current source; a saturable reactor; a series asymmetrically conducting device; a shunting asymmetrically conducting device; a make-alive circuit including, in series-circuit relation, said alternating-current source, said saturable reactor, said series asymmetrically conducting device, and a make-alive electrode ofsaid valve-device, whereby unidirectional-current impulses of one polarity are delivered, through said series asymmetrically conducting device, to said make-alive electrode; and a shunting circuit, including said shunting asymmetrically conducting device, coning a. saturable core; a series asymmetrically conducting device; a shunting asymmetrically conducting device; circuit-means, including said alternating-current source, for impressing upon said inductance-device an alternating voltage having substantially equal positive and negative impulses, the magnitude of said impulses being sufllcient to saturate the inductance-device at a portion of each of the positive and negative imq pulses, whereby a discontinuity in the saturationcurve of the inductance-device is obtained at said portion of each ositive and negative impulse; a current-supplying circuit-means, including said series asymmetrically conducting device, for utilizing said inductance-device to cause peaked positive current impulses to be supplied to a load-device; and a. shunting circuit, including said shunting asymmetrically conducting device, connected in shunt-circuit relation around said load device and said series asymmetrically conducting device, whereby a path is provided for the peaked negative current-impulses.

4. A control system comprising, an alternatingcurrent source; an inductance-device having a saturable core; a capacitor; a series asymmetrically conducting device; a shunting asymmetrically conducting device; circuit-means, including said alternating-current source; and also including said capacitor and said inductance'device, for impressing upon said inductance device an alternating voltage having substantially equal positive and negative impulses, the magnitude of the impulses being sufficient to saturate the inductance-device at a portion of each of the.

'1 each positive and negative impulse; said capacitor and said inductance device being connected in series for controlling the shape and duration of the current impulses, a current-supplying circult-means, including said series asymmetrically conducting device, for utilizing said inductance-device to cause peaked positive currentimpulses to :be supplied to a load-device; and a shunting circuit, including said shunting asymmetrically conducting device, connected in shuntcircuit relation around said load device and said series asymmetrically conducting device, whereby a. path is provided for the peaked negative current-impulses.

WIILIAM E. PAKALA. 

